Audiology Chapter 11 – Auditory Nerve & Central Auditory Pathways

Vocabulary flashcards summarizing key terms, structures, disorders, tests, and management concepts from Chapter 11 on the auditory nerve and central auditory pathways.

Central Auditory System

All neural structures from the auditory nerve through the brainstem, midbrain, thalamus, and auditory cortex that analyze and interpret sound.

Intrinsic Redundancy

Multiple parallel neural pathways within the auditory system that repeatedly analyze an acoustic signal, providing built-in backup for accurate perception.

Extrinsic Redundancy

Redundant information contained in speech itself (syntax, semantics, context) that aids understanding even when parts of the signal are degraded.

Internal Auditory Canal (IAC)

Bony canal running from the cochlear modiolus to the brainstem that carries the vestibulocochlear nerve, facial nerve, and internal auditory artery.

Vestibulocochlear Nerve (Cranial Nerve VIII)

Sensory nerve containing ~30,000 auditory and ~20,000 vestibular fibers that transmits hearing and balance information to the brain.

Facial Nerve (Cranial Nerve VII)

Motor/sensory nerve that shares the internal auditory canal with CN VIII; controls facial muscles and transmits taste from the anterior tongue.

Tonotopic Organization

Spatial arrangement where nerve fibers or brain regions are ordered by frequency: high frequencies lateral/basal, low frequencies medial/apical.

Basal (High-Frequency) Fibers

Auditory nerve fibers originating at the base of the cochlea; located on the outer portion of the nerve bundle and code high-pitched sounds.

Apical (Low-Frequency) Fibers

Auditory nerve fibers from the apex of the cochlea; lie in the inner portion of the nerve bundle and code low-pitched sounds.

Cerebellopontine Angle (CPA)

Junction of cerebellum, pons, and medulla where the auditory and vestibular nerves separate; common site of acoustic neuromas.

Decussation

A crossover point in the brain where neural fibers cross to the opposite side.

Commissure

A bundle of nerve fibers connecting similar structures on the two sides of the brain.

Ipsilateral

Located on or affecting the same side of the body.

Contralateral

Located on or affecting the opposite side of the body.

Cochlear Nucleus

First brainstem nucleus receiving auditory‐nerve input; divided into dorsal and ventral divisions.

Dorsal Cochlear Nucleus

Portion of the cochlear nucleus involved in complex spectral analysis of sound.

Ventral Cochlear Nucleus

Portion of the cochlear nucleus important for precise timing information and relay to higher centers.

Trapezoid Body

Pons structure where many auditory fibers decussate; initiates bilateral representation of a signal from one ear.

Superior Olivary Complex (SOC)

Brainstem nucleus receiving input from both ears; analyzes interaural time and intensity cues for sound localization and mediates acoustic reflexes.

Lateral Lemniscus

Major fiber tract carrying signals from both SOCs to the inferior colliculus in the midbrain.

Inferior Colliculus

Midbrain auditory center integrating inputs from lower brainstem nuclei before relay to the thalamus.

Medial Geniculate Body (MGB)

Thalamic relay for auditory information; its ventral division projects to the auditory cortex.

Auditory Radiations

Fiber pathways carrying signals from the MGB to the auditory cortex in the temporal lobe.

Heschl’s Gyrus (Superior Temporal Gyrus)

Primary auditory cortex on the temporal lobe where conscious perception of sound occurs.

Sensorineural Hearing Loss (SNHL)

Hearing loss arising from damage to the cochlea or auditory nerve; typically permanent.

Tinnitus

Perception of sound (ringing) without external stimulus; often an early sign of auditory-nerve pathology.

Acoustic Neuroma

Benign tumor (vestibular schwannoma) arising in the internal auditory canal, potentially compressing CN VIII and adjacent structures.

Vestibular Schwannoma

Alternative term for acoustic neuroma, emphasizing origin from Schwann cells of the vestibular nerve.

Performance-Intensity Rollover

Decline in word-recognition scores at high presentation levels; may indicate retrocochlear lesions such as acoustic neuroma.

Acoustic Neuritis

Inflammation of the auditory portion of CN VIII causing sudden SNHL and possible vertigo.

Multiple Sclerosis (MS)

Demyelinating disease that can disrupt auditory nerve conduction leading to neural hearing difficulties.

Auditory Neuropathy Spectrum Disorder (ANSD)

Condition with normal outer hair cell function but dyssynchronous firing of CN VIII, producing mild-moderate SNHL and poor speech recognition.

Central Deafness

Rare bilateral cortical or subcortical damage causing profound auditory impairment despite intact ears.

Central Auditory Processing (CAP)

Efficiency and effectiveness with which the central nervous system uses auditory information.

Central Auditory Processing Disorder (CAPD)

Deficit in neural processing of auditory stimuli not explained by higher-order cognitive or language factors.

Sound Localization

Ability to determine origin of sound in space, relying on interaural time and intensity cues processed by the SOC.

Auditory Discrimination

Skill of distinguishing differences between sounds such as phonemes or pitches.

Temporal Processing

Processing of timing aspects of sound, including gap detection, duration, and rhythm.

Auditory Figure-Ground

Ability to understand speech in the presence of competing noise.

Auditory Closure

Skill in filling in missing or degraded speech information to grasp meaning.

Binaural Integration

Dichotic listening ability to combine different signals presented simultaneously to each ear.

Binaural Separation

Dichotic listening ability to focus on and repeat the signal from one ear while ignoring the other.

Executive Functions

Cognitive processes—attention, planning, inhibition, memory—controlling goal-directed behavior.

Phonemic Decoding

Brain’s ability to break down and interpret speech sounds for reading and spelling.

Masking Level Difference (MLD)

Binaural interaction test measuring improved signal detection when noise and signal are out of phase between ears.

Gaps-in-Noise Test

Temporal patterning test assessing the smallest silent interval a listener can detect in noise.

Dichotic Digits Test

Assessment where different numbers are presented to each ear simultaneously to evaluate binaural integration/separation.

Staggered Spondaic Word (SSW) Test

Dichotic test presenting overlapping spondaic words to assess auditory processing abilities.

Synthetic Sentence Identification (SSI)

Speech test using low-context sentences with competing messages to evaluate monaural or dichotic listening.

Filtered Speech Test

Monaural speech test presenting spectrally degraded words to assess auditory closure skills.

Auditory Evoked Potentials (AEPs)

Electrical responses from the auditory pathway measured via electrodes; include ABR, middle latency, and cortical responses.

Wave I Latency Delay

Prolonged timing of ABR wave I suggesting outer, middle, or inner ear lesion.

Wave III Latency Delay

Prolonged ABR wave III indicating auditory nerve or lower brainstem lesion.

Wave V Latency Delay

Prolonged ABR wave V pointing toward higher brainstem pathology.

Otoacoustic Emissions (OAEs)

Sounds generated by outer hair cells; presence indicates normal cochlear outer hair cell function.

FM (Frequency-Modulated) System

Assistive listening device transmitting teacher’s voice directly to listener, reducing background noise.

Comorbidity

Coexistence of two or more disorders within the same individual, common between CAPD and ADHD or language disorders.

Preferential Seating

Environmental modification placing a listener close to the sound source to improve auditory access.

Metacognitive Techniques

Strategies like chunking and step-by-step processes that help individuals manage auditory information more effectively.

Multidisciplinary Team

Collaboration of audiologists, speech-language pathologists, psychologists, and educators in diagnosing and managing CAPD.

Binaural Fusion

Perceptual phenomenon where slightly different signals to each ear are combined into a single auditory image.

Rapidly Alternating Speech Perception (RASP)

Test presenting brief speech segments alternating between ears to evaluate auditory temporal and interhemispheric processing.

Temporal Durations Patterns Test

Assessment requiring identification of long and short tone sequences to measure temporal pattern recognition.